Immunoassays for Food-poisoning Bacteria and Bacterial Toxins

Transcription

1 Immunoassays for Food-poisoning Bacteria and Bacterial Toxins

2 FOOD SAFETY SERIES General Series Editors J. Edelman London, UK S. Miller Texas, USA Series Editor - Microbiology T. Roberts Reading, UK Editorial Board D. Conning London, UK D. Georgala Reading, UK J. Houtvast Wageningen, The Netherlands C. Mercier Paris, France E. Widdowson Cambridge, UK Forthcoming Titles Food Reactions M. Lessof The Staphylococci and their Toxins M. Bergdoll The Aeromonas Group as a Foodborne Pathogen S. Palumbo and F. Busta Food Preservation G. Gould Fibre and Complex Carbohydrates I. Johnson and D. Southgate

3 Immunoassays for F ood -poisoning Bacteria and Bacterial T oxins G. M. Wyatt with contributions from H. A. Lee and M. R. A. Morgan AFRC Institute of Food Research, Norwich, UK JAMES JAMES Springer-Science+Business Media, B.V.

4 First edition G. M. Wyatt, H. A. Lee and M. R. A. Morgan Originally published by Chapman & Hall in 1992 Typeset in 12/13pt Garamond 3 by Columns of Reading Ltd Softcover reprin t of the hardcover 1 st edi tion 1992 ISBN DOI / ISBN (ebook) Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the UK Copyright Designs and Pateots Act, 1988, this publication may not be reproduced, stored, or rransmitted, in any form or by any means, without the prior permission in wriring of rhe publishers, or in rhe case of reprographic reproducrion only in accordance with the terms of licences issued by the Copyright Licensing Agency in the UK, or in accordance with the terms of licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be seot to the publishers at the London address prioted on this page. The publisher makes no representarion, express or imp1ied, with regard to the accuracy of the informat ion cootained in this book and cannot accept any legal responsibility or liability for any errors or omissions that may be made. A catalogue record for this book is available from the British Library Library ofcongress Cataloging-in-Publication data available

5 Contents List of figures Series introduction Acknowledgement Preface VIlI Xl XIl XIIl 1 Introduction 1 2 Food-borne bacteria Intoxications by pre-formed toxin 6 2. l. 1 Staphylococcus au reus 6 2.l.2 Bacillus cereus 7 2.l.3 Clostridium botulinum Infections Salmonellae Escherichia coli Clostridium perfringens Vibrios Shigellae Campylobacters Listeria monocytogenes Other organisms Antigenic structures Bacterial toxins Bacterial cells 15 v

6 CONTENTS 3 Historical aspects Use of antibodies in microbiology Traditional culture methods for bacteria Detection of toxins by traditional methodology A new perspective on detection of bacteria? 24 4 Food as an assay matrix Physical and chemical properties of food Microbial flora of food 28 5 Antibody technology Immunization protocols Polyclonal antibodies Monoclonal antibodies Antibody production by genetic manipulation techniques Analyte-antibody binding mechanisms Phase separation systems End-point detection systems Immunoassay formats ELISA Latex agglutination methods Microscopy using labelled antibodies Flow cytometry Cell concentration methods Immunosensors Signal amplification in ELISAs Application to food samples 67 6 Equipment and instrumentation Equipment available Data gathering, storage and processing 76 7 Assessment of assay performance Sources of error in assays Validation and quality control Relative costs of immunoassays Limitations of immunoassays 84 Vi

7 CONTENTS 8 Assays available commercially 8.1 ELISAs 8.2 Other formats 9 Conclusions 9.1 Critical comparison with other methods 9.2 Future impact of new technology Impact on public health Impact on industrial practice Appendices 96 1 Definition of terms used 96 2 Hapten conjugation methods 99 3 Preparation of antigenic structures from bacterial cells Monoclonal antibody techniques Enzyme/substrate systems Antibody labelling methods Immunoassay reagents and methods Preparation of immunoaffinity columns Suppliers of equipment and consumables 113 References 120 Index 124 VIl

8 List of Figures Figure 1.1 Figure 2.1 Figure 2.2 Figure 5.1 Figure 5.2 Figure 5.3 Figure 5.4 Figure 5.5 Figure 5.6 Figure 5.7 Figure 5.8 Figure 5.9 Figure 5.10 Figure 5.11 Figure 5.12 Figure 5.13 Figure 5.14 Figure 5.15 Figure 5.16 Figure 5.17 Figure 5.18 Newspaper stories on food-poisoning incidents Surface structures of Gram-negative cells Surface structures of Gram-positive cells Structure of IgG molecule An outline of monoclonal antibody production A robotic system for handling hybridoma cell culture Antibody gene clusters The polymerase chain reaction Determination of antibody affinity Cross-reactivity in assays Microtitration plates Principles of limited-reagent assays Principles of excess-reagent assays Typical titration curve for a polyclonal antiserum Typical standard curve for a limited-reagent assay Typical standard curve for a sandwich assay Calculation of cross-reactivity Principle of homogeneous immunoassay Flow cytometry Immunoconcentration methods Immunosensors Vlll

9 LIST OF FIGURES Figure 5.19 Figure 5.20 Figure 5.21 Figure 5.22 Figure 6.1 Figure 6.2 Figure 6.3 Figure 6.4 Figure 7.1 Figure 7.2 Figure 8.1 The avidin-biotin amplification system Enzyme cycling amplification system Selective enrichment culture for pathogenic bacteria IFR protocol for salmonella detection A range of plunger-type pipettes Semi-automatic plate washer Automatic plate washer Microtitration plate reader Superimposable standard curves The precision profile Presentation of commercial assay kit IX

10 Series Introduction Consumer safety has become a central issue of the food supply system in most countries. It encompasses a large number of interacting scientific and technological matters, such as agricultural practice, microbiology, chemistry, food technology, processing, handling and packaging. The techniques used in understanding and controlling contaminants and toxicity range from the most sophisticated scientific laboratory methods, through industrial engineering science to simple logical rules implemented in the kitchen. The problems of food safety, however, spread far beyond those directly occupied in food production. Public interest and concern has become acute in recent years, alerting a wide spectrum of specialists in research, education and public affairs. This series aims to present timely volumes covering all aspects of the subject. They will be up-to-date, specialist reviews written by acknowledged experts in their fields of research to express each author's own viewpoint. The readership is intended to be wide and international, and the style to be comprehensible to non-specialists, albeit professionals. The series will be of interest to food scientists and technologists working in industry, universities, polytechnics and government institutes; legislators and regulators concerned with the food supply; and specialists in agriculture, engineering, health care and consumer affairs. One of the most difficult situations to control is the contamination of food by small numbers of pathogenic micro-organisms before they multiply to give the large populations causing food poisoning when eaten. A rapid detection method would be of immense value to food producers and retailers, to public analysts and legislators as well as benefiting the public at large at a time when the reported incidence of food poisoning appears to be rising year by year. This book, by Drs Wyatt, Lee and Morgan, describes the current state of research into the powerful and elegant techniques of immunoassay as a means of dealing with this microbiological problem. ]. Edelman Xl

11 Acknowledgement The authors wish to acknowledge the Photography Section at the Institute of Food Research, Norwich for excellent preparation of the figures, and Mrs Janet Arnett for careful typing of the manuscript. Xll

12 Preface This book is intended to be a compilation or distillation of current knowledge of the subject, and most of the material in it is within the experience of the authors. Where necessary, specific references to the literature have been made; otherwise a bibliography is given at the end of the appropriate chapter. In order not to interrupt the flow of the text, detailed methodology has been consigned to a series of appendices. XUl